Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

VET200 SEM 1 > EXCITABLE CELLS > Flashcards

EXCITABLE CELLS Flashcards

1
Q

define current

A

Net movement of charge between two places, measured in Amperes (amps, I)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

When does current flow?

A

Current will flow if two places with a potential difference are connected by a conductor -> current carried via ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

why is ion movement restricted by cell membranes?

A

ions cannot diffuse, repelled by hydrophobic phospholipid tails

Ions must cross via channels/carriers (integral membrane proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is a channel protein?

A

Transmembrane protein with a hole (pore) in the middle

  • don’t saturate -> dependent on ion concentrations
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Two types of channel proteins

A
  1. Leak channel -> open all the time
  2. gated channel -> only open in response to stimuli
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is a carrier protein?

A

Transmembrane proteins that change shape (conformation)

  • saturate -> dependent on availability of binding sites
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Conc of Na+, K+, Cl- and Ca2+ across cell membranes

A

Na+ = high outside
K+ = high inside
Cl- = high outside
Ca2+ = high outside

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Define membrane potential (Vm)

A

difference in charge (potential difference) between inside and outside of a cell at any point of time

  • constantly changing in excitable cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

defne membrane current

A

Movement of charge ions between inside and
outside of the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Two gradients driving currents

A
  1. Chemical -> ion concentration
  2. Electrical -> opposite charges attract, like repell. ion movement according to overall charges/interaction between charge on ion and charge in inside of cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

define electrochemical gradient

A

overall force on an ion due to combination of chemical and electrical driving forces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is Equilibrium potential (Ex)

A

value of Vm at which electrical gradient is EQUAL in magnitude and OPPOSITE in direction to the chemical gradient —> NO NET MOVEMENT OF ION

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what would (theoretically) happen if a cell was only permeable to one cell and ion channels were open

A
  • ion movement occurs until ion is at equilibrium
  • Vm will be equal to equilibrium potential for that ion
  • no ne ion movement
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is resting membrane potential?

A
  • overall voltage across the cell membrane when the cell is not transmitting an electrical signal
  • no net movement -> ions into and out of cell are equal
  • observed in all cells, excitable and non-excitable
  • usually negative inside -> membrane most permeable to K+ ions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are membrane pumps?

A

carriers with special enzymatic activity that can use energy from ATP hydrolysis to move ions against their electrochemical gradient
- RMP is stabilised by active transport: the Na+/K+ ATPase pump -> needed because naturally K+ will leave the cell and be depleted eventually

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

do all cells have a resting membrane potential?

A

Yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is an excitable cell?

A

cells that use electricity to transmit signals -> transmit rapidly over long distances
- transmit electrical signals by changing their membrane potential (Vm) -> constantly changing in excitable cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

define depolarisation, repolarisation and hyperpolarisation

A

depolarisation -> Vm more positive than RMP (pos ions in)
Hyperpolarisation -> Vm more negative than RMP (pos ions out)
Repolarisation -> Vm returning towards RMP following depolarisation/hyperpolarisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

how are signals sent through nervous system -> define a synapse

A
  • electrical signals transmitted through neurons
  • chemical and electrical signals transmitted bettween neurons -> over a synapse (site of communication between two excitable cells)
20
Q

what are graded and action potentials?

A
  • electrical signals
  • graded = input signals, small changes in membrane potential in response to a stimulus (stimulus gated ion channel)
  • action = output signals
  • both involve opening or closing gated ion channels
21
Q

How is an action potential generated?

A
  • large stimulus generates large graded potential
  • graded potential reaches threshold and remains above threshold despite currrent leakage
  • voltage-gated channel opens and AP fires
  • AP opens more voltage-gated channels, AP spreads
22
Q

what are some graded potential properties?

A
  1. can be hyper polarising or depolarising
  2. amplitude depends on stimulus amplitude -> larger stimulus = more gated ion channels opened, more ions = bigger graded potential
  3. Multiple graded potentials can summate -> add together
  4. amplitude decreases with distance from the stimulation site
23
Q

two types of graded potential summation:

A
  1. temporal summation -> adding two or more graded potentials generated by the same input close together in time
  2. spatial summaton -> Adding together of two or more graded potentials generated by different inputs
24
Q

What occurs during an AP

A
  1. passive spread of current from AP firing site opens VGSCs in adjacent membrane -> a sequence of ion channel opening and ion movements that occurs in EXACTLY THE SAME WAY EACH TIME threshold is reached
    - involve a period of depolarisation followed by a period of repolarisation
    - The exact sequence of ion movements varies between excitable cell types
25
What are the 3 phases of nerve action potentials?
1. depolarisation 2. repolarisation 3. hyperpolarisation
26
what is the effect of threshold on voltage gated sodium channels and potassium (K) channels
1. opening of VGSC activation gate (fast) 2. closure of VGSC inactivation gate (slow) 3. Opening of VGKC (slow) * sodium channels open more quickly = few milliseconds where Na+ flows into cell before K+ flows out of cell = increased positive (upstroke of AP)
27
what are the ion movements during 3 phases of an action potential?
1. Resting membrane potential - Na+ activation agate closed - Na+ inactivation gat open - K+ actvation gate closed 2. Depolarisation Phase - Na+ activation gate open - Na inactivation open - K+ activated gate closed - Na+ depolarises membrane 3. repolarisation phase - Na+ activation open - Na inactivation closed - K+ activation open - K+ efflux repolarises membrane 4. Hyperpolarisation Phase - Na+ activattion gate closed - Na inactivation open - K+ activation open - sustained K+ efflux hyper-polarisation beyond RMP -> stops AP
28
properties of APs
1. always depolarising (followed by a period of hyper polarisation) -> can't form AP from hyperpolarisation 2. amplitude is INDEPENDENT OF STIMULUS AMPLITUDE -> within a given cell, AP always same amplitude (fixed) 3. cannot summate -> 4. amplitude does not change with distance from the stimulation site -> spread metres without decreasing in amplitude
29
compare graded and action potentials:
graded: - function = input signal - site = dendrites, soma - ion channels involved = gated ion channels (ligand, voltage, mechanical) - properties = depolarising or hyperpolarsising, amplitude dependent of stimulus, summate, amplitude diminishes further from stimulus Action: - function = output signal (long distance conduction) - site = axon hillock, axon - channels involved = voltage gated ion channels - properties = depolarisng, amplitude independent of stimulus amplitude, don't summate, stay constant over long distances
30
What two properties of axons increase conduction velocity?
1. increased diameter of axon -> increases both leak current and axonal current (more so axonal) 2. myelination of axon
31
what is passive vs active current
passive = charge transfer active = membrane currents due to channel opening
32
is passive or active current faster
- passive
33
what affects the passive current flow
1. leak current (IL) = out 2. Axonal current (IA) = forward
34
explain effect of increasing axon diameter
- increases both leak and axonal current -> but more axonal - IA proprtional to r squared - IL proportional to r - increased radius = increased number of leak channels -> but also increased cytoplasm for current to flow
35
explain effect of increasing myelin
- sheath acts as electrical insulator - reduces current leakage - increase in AP velocity - myelin = lipid bilayer - nodes of ranvier = sections of axon not covered in myelin - when myelinated, VGSCs only opened at nodes so APs jump between node to node (saltatory conduction) -> unmyelinated must open sequential VGSCs along axon (slow)
36
In wha way do APs change in response to stimulus?
- Above-threshold stimuli always generate APs of the same amplitude - Stimulus strength is reflected in AP rate not AP amplitude (stronger stimuli lead to higher frequency AP firing, not bigger APs
37
What is the absolute refractory period?
- occurs during depolarisation phase - immediately after first AP, second Ap cannot be initiated - VGSC inactivation gate is closed, Na+ cant enter cell, must wait for it to spontaneously open again before firing another AP (due to channel kinetics)
38
What is the Relative refractory period?
- occurs during hyper polarisation phase (end) - second AP can only be initiated by bigger than usual stimulus -> because cell has become very negative - VGKCs are still open, continuing K+ efflux, membrane is hyper polarised, need bigger stimulus to get to threshold
39
What are the parts of the chemical synapse
1. presynaptic neuron -> neuron sending signal 2. postsynaptic neuron -> neuron receiving signal 3. synaptic cleft -> gap between pre and post synaptic neurons 4. nerve terminals -> specialised regions at the end of the axon 5. Neurotransmitter -> chemicals released from nerve terminals 6. synaptic vesicles -> lipid bilayer spheres that store neurotransmitters 7. Receptors -> ligand-gated proteins in the postsynaptic membrane
40
Basic steps in chemical synaptic transmission
1. action potential in terminal opens voltage-gated calcium channels 2. calcium entry triggers exocytosis of synaptic vesicles 3. transmitter released during exocytosis binds to postsynaptic receptors, producing postsynaptic response
41
agonist vs antagonist
- agonist binds to receptor and induces a response in target cell - antagonist binds to receptor but won't induce response *may compete with one another to occupy receptors*
42
What are the classes of postsynaptic receptors and compare?
1. Ionotropic -> fast postsynaptic response - ligand-gated ion channels - neurotransmitters binding will open channel - allow ion to move across membrane = graded potential 2. Metabotropic -> produce more complex response but slower - neurotransmitter binds to receptor that is coupled to G protein - G protein modulates ion channels directly or indirectly via intracellular effector enzymes and/or second messengers —> graded potential - slower process because it is 5 steps long
43
What are EPSPs and IPSPs?
E = excitatory postsynaptic potentials that drive Vm toward threshold, increasing probability of AP firing in post synaptic cell I = inhibitory, keep Vm away from threshold
44
why is terminating the transmission of a signal needed:
- must remove transmitter from synaptic cleft - needed to maintain temporal (timing) precision of signals and prevents receptor desensitisation
45
3 ways of removing transmitters
1. transmitter reuptake (most common) 2. enzymatic degradation of transmitter -> primarily at synapses that release acetylcholine (fastest) 3. Diffusion - all synapses to some extent

VET200 SEM 1 (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions